Unvulcanized rubber and compounding ingredients therefor are often packaged by wrapping with thermoplastic film or placing in bags thereof. Polyethylene is conventially used because of its plasticity, antiblock property, because it can be obtained in a desirable melting temperature range and at a relatively low cost.
However, polyethylene is disadvantageous because, when mixed with unvulcanized rubber, does not disperse sufficiently in the matrix. This leaves minute areas within the matrix of the rubber when cured, which are themselves not cured and are subject to degradation.
Various solutions have been proposed. Very low softening point polyethylene has been used. Compounded elastomeric styrene/butadiene/styrene block copolymer films have been used with success but are considerably more costly than polyethylene and sometimes do not provide an effective packaged article when its contents include oil of the rubber-processing type. Although it has not been fully ascertained, it appears that films of ethylene/vinyl acetate copolymers containing about 28-30% vinyl acetate have been used although the inventors' evaluation of such films has indicated them to be generally unsatisfactory and without sufficient strength under test to package and contain rubber compounding ingredients, particularly when containing a rubber processing oil.
Therefore, it is an object of this invention to provide packaged materials for compounding rubber with a suitable film and to provide rubber compounded with such a package.